title: Effects of erythropoietin on intracellular calcium concentration of rat primary cortical neurons.
abstract: Erythropoietin (Epo) has been shown to afford neuroprotection in many experimental models. Although the cytosolic Ca(2+) concentration ([Ca(2+)](i)) is an important factor regulating cell survival, the effects of Epo on [Ca(2+)](i) in neurons are not fully elucidated. We studied the effects of human recombinant Epo on [Ca(2+)](i) of rat primary cortical neurons in normal and excitotoxic conditions. Changes in [Ca(2+)](i) were measured using fura-2 microfluorometry in rat primary cortical cultures. In the control condition with 2mM Mg(2+) in the bath solution, Epo at 4 u/ml significantly increased the fluorescence ratio, but the Epo-induced increase in the fluorescence ratio was abolished by omission of Ca(2+) from the bath solution and by the addition of cadmium. Omission of Mg(2+) and supplementation with glycine resulted in basal and periodic increases in the fluorescence ratio, due to sustained activation of N-methyl-d-asparate (NMDA) receptors. Epo at 0.4 and 4 u/ml significantly decreased the fluorescence ratio in this condition, and this effect was attenuated by the phosphoinositide 3-kinase (PI3K) inhibitors, LY 294002 and wortmannin, and the Ca-activated K channel blocker, iberiotoxin. In the presence of Mg(2+) and exogenous glutamate, 4 but not 0.4 u/ml Epo slightly but significantly reduced the [Ca(2+)](i) elevation. These results suggest that Epo increased [Ca(2+)](i) in cortical neurons by inducing Ca(2+) entry in the control condition but decreased [Ca(2+)](i) in the Mg(2+)-free excitotoxic condition, at least in part via PI3K-dependent activation of Ca-activated K channels. Reduction of [Ca(2+)](i) by Epo in the excitotoxic condition may contribute to neuroprotection.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Yokohama City University Graduate School of Medicine, Japan. psdelico06@yahoo.co.jp
authors.forename: Tomio
authors.initials: T
authors.lastname: Andoh
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Echigo
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Michiko
authors.initials: M
authors.lastname: Hayashi
authors.forename: Ichidai
authors.initials: I
authors.lastname: Kudoh
authors.forename: Takahisa
authors.initials: T
authors.lastname: Goto
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D004921:Erythropoietin / Q000378:metabolism* / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000494:pharmacology; D016257:Fura-2 / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D009474:Neurons / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins
chemical_list: D015220:Calcium Channels; D005456:Fluorescent Dyes; D018696:Neuroprotective Agents; D011994:Recombinant Proteins; D004921:Erythropoietin; D002118:Calcium; D016257:Fura-2